Long-range Coulomb interactions in small Si devices. Part II. Effective electron mobility in thin-oxide structures

In metal-oxide-semiconductor structures with polycrystalline Si gates, elec trons in the inverted channel of the substrate scatter with electrons in th e gate via long-range Coulomb interactions. For thin oxides, these interact ions can cause a significant transfer of momentum from the channel to the g ate, thus reducing the effective mobility of the two-dimensional electron g as in the substrate. We present calculations of the dispersion of the inter face plasmons in poly-Si/SiO2/Si structures, comparing the results obtained in the long-wavelength limit to those obtained using the random-phase appr oximation. Employing the former model, we compute the effect of plasmon sca ttering on the effective electron mobility in Si inversion layers. We find a significant reduction of the mobility for oxides thinner than about 3 nm. (C) 2001 American Institute of Physics.